1. Field of the Invention
The present invention relates to a technique of controlling a playback operation of a DVD-Video disk.
2. Description of the Related Art
In the art, a DVD-Video player is known as an apparatus for playing back a DVD-Video disk on which video content is recorded, and a DVD-Audio player is known as an apparatus for playing back a DVD-Audio disk on which audio content is recorded.
The DVD-Video disk refers to a storage medium on which content has been recorded in accordance with the DVD-Video standard, and the DVD-Audio disk refers to a storage medium on which content has been recorded in accordance with the DVD-Audio standard. The DVD-Video standard and the DVD-Audio standard are similar in the physical specifications and the file format specifications. However, there is some difference between them in the application specifications, although the application specifications are also similar in many parts to achieve maximum possible compatibility between them.
The DVD-Audio disk is allowed to include not only audio content but also video content. When video content is recorded on a DVD-Audio disk, it is recorded in a format which allows a DVD-Video player to play it back. An audio part of video content recorded on a DVD-Audio disk can be played back by a DVD-Audio player.
FIG. 24 shows the manner in which video presentation data and audio presentation data are recorded on a DVD-Audio disk.
Each DVD-Audio disk has a video zone and an audio zone. In the audio zone, the audio content, as denoted by AUDIO in FIG. 24, is stored according to the DVD-Audio standard. In the video zone, the video content is stored according to a standard which is based on the DVD-Video standard but which has some restrictions (a subset of the DVD-Video standard), as denoted by VIDEO in FIG. 24.
This allows DVD-Video players to play back video content stored, according to the subset of the DVD-Video standard, in the video zone of a DVD-Audio disk. The video content refers to content including a moving picture and sound/voice.
The video content is constructed in the following format. That is, each video content includes one or more video titles (VTTs), each of which includes one or more program chains (PGCs), wherein each PGC defines the order in which to play back one or more programs PG. Each PG includes one or more video title set (VTS) cells each of which includes one or more video object set units (VOBUs), wherein each VOBU includes moving image data (V-packs) and audio data (A-packs)
The DVD-Video player controls the order in which PGCs are played back and plays back PGs in the order defined by each PGC, thereby playing back video content including moving picture data and audio data in units of video titles or in other units.
On the other hand, the audio content is constructed in the following format. That is, each audio content includes one or more audio titles (AOTTs) and no or one or more audio with video titles (AVTTs)
Each AOTT includes one or more program chains (PGCs) each of which defines the order in which programs are played back. PGs in each AOTT can be of one of two types described below.
One PG type is a PG including one or more audio title set (ATS) cells each of which includes one or more audio object set units (AOBUs), wherein each AOBU includes audio data (A-packs). When PGs of this type are played back, audio data of A-packs in AOBUs of ATS cells are played back.
The other PG type is a PG which does not include ATS cells but which includes pointers pointing to VTS cells in a video zone. When this type of PG is played back, audio data of A-packs of VOBUs of VTS cells pointed to by the pointers are played back.
Each AVTT includes one or more PGCs each of which defines the order in which one or more PGs are played back. Each PG in an AVTT points to a VTS cell in the video zone. When a PG of this type is played back, moving image data (V-packs) and audio data (A-packs) in VOBUs of the VTS cell pointed to by the PG are played back. However, to play back the moving image data in AVTTs by a DVD-Audio player, the DVD-Audio player needs to have a capability of playing back video data.
In each audio content, a group Gr including one or more AOTTs and tracks corresponding to PGs are defined. The DVD-Audio player plays back audio data in AOTTs or AVTTs by playing back PGs in PGCs or playing back PGs corresponding to tracks in a Gr specified by a user. In the case in which the DVD-Audio player has the capability of playing back video data, moving image data and audio data in AVTTs can also be played back by playing back PGs in accordance with respective PGCs or by playing back PGs corresponding to groups or tracks specified by a user.
As described above, a DVD-Audio disk is allowed to include video content, according to the DVD-Video standard, in the video zone thereof, and audio data in the video zone can be played back by DVD-Audio players. However, if audio data of the video content recorded on a DVD-Video disk according to the DVD-Video standard is attempted to be played back using a DVD-Audio player, which does not have the capability of playing back video data, in a similar manner to the manner in which audio data recorded in the video zone of a DVD-Audio disk is played back, the following problems can occur.
That is, in the DVD-Video standard, it is allowed to define a menu with a combination of moving picture data, still picture data, and button data so that when a DVD-Video disk is played back, the menu is displayed in accordance with the definition described on the DVD-Video disk so as to prompt a user to enter an operation command on the menu. In some cases, when a DVD-Video disk is used, displaying such a menu and a user operation on the menu are indispensable to starting playback and/or continuing playback. For example, in the case of a DVD-Video disk including definition information indicating that a title menu should first be displayed after playback of the DVD-Video disk is started and a title specified by a user should be performed, it is required that the user should first select a title on the title menu to use the DVD-Video disk.
However, DVD-Audio players according to the DVD-Audio standard do not have the capability of displaying such a menu and receiving a selection command from the menu. DVD-Audio players cannot even display a menu including moving picture data, unless the DVD-Audio players have the capability of playing back video data. In many cases, DVD-Audio players dedicated to playing back DVD-Audio disks do not even have a display capable of displaying such a menu.
Therefore, for DVD-Audio players which do not have the capability of displaying a menu, it is often impossible to play back audio data recorded on a DVD-Video disk.
When a user tries to play back only audio data recorded on a DVD-Video disk by a DVD-Video player, if a menu cannot be displayed, as in the case in which no display is connected to the DVD-Video player or the display connected to the DVD-Video player does not satisfy necessary specifications, it is impossible to play back audio data.
Even when a user tries to play back a DVD-Video disk in a situation in which a menu can be correctly displayed on a display connected to a DVD-Video player, if users do not know how to handle the DVD-Video player, which may occur when users are very young or very old, or if users cannot understand a menu, which may occur when the menu is displayed in a foreign language the users cannot understand, the DVD-Video disk cannot be played back. Also, in a case in which a user cannot operate a menu for some reason, a DVD-Video disk cannot be played back.
The above-described problems occur not only in DVD-Video disks, but similar problems can occur when using a storage medium according to any standard which requires displaying a menu or the like and performing a selection operation on the menu to start and/or continue playing.